Dr. T. Ombrello - UCC Biology Department

MADAGASCAR PERIWINKLE

Common names:

Madagascar Periwinkle, Rose Periwinkle, Periwinkle, Vinca, Old-Maid

Scientific name: Catharantus roseus

Explanation of scientific name:

Catharantus - Greek for clean or pure flower

roseus - Latin for rose-colored

Annual bedding plants seem to go in and out of fashion over the years. Gardeners always yearn for something “new” or “different” and become bored with some species even though they perform well in the garden. At one time petunias were the top selling annuals. Today that distinction is held by impatiens. While no one can tell what will be in vogue next, a contender might be the Madagascar Periwinkle.

By no means a new species, the Madagascar Periwinkle has been grown in this country since the 19^th century. Many do not know it because of its many common names that are also applied to other species, causing confusion. Even its scientific name, Catharantus roseus, causes problems since the species used to be known as Vinca rosea.

While the name may be perplexing, few question its beauty in the landscape. Glossy, dark-green leaves on stems 3 – 18 inches tall (depending on cultivar) provide a perfect background for the single phlox-like flowers in shades of rose, pink, and white. Blooms are produced continuously from June until frosts in the fall. Madagascar Periwinkles thrive in full sun or partial shade. They tolerate dry soils, but do poorly on wet sites. The evenly moist soil of a typical annual garden suits them best. Their tropical ancestry dictates a need for warmth, and experienced gardeners do not set them out too early in the spring. Compared to other annuals, they are slow growing from seed and must be sown in February in order to have reasonably sized plants in May. They can also be rooted from cuttings. Essentially free of insects and diseases, even deer avoid them in favor of other annuals.

The renewed interest in Madagascar Periwinkle is the result of successes in plant breeding. Hybridizers have been working with Madagascar Periwinkle for decades, with the cultivar ‘Polka Dot’, a dwarf trailing type, winning a prestigious All-American Selection Award in 1969. Work at the University of Connecticut, crossing the Madagascar Periwinkle with its rare wild relatives produced an almost unheard of 3 All America Selection Award winners in 1991; ‘Pretty in Pink’, ‘Pretty in Rose’, and ‘Parasol’. They have flowers several times larger than any previous type. New cultivars are released regularly, increasing the popularity of the species.

The Madagascar Periwinkle’s value is not limited to ornamentation. Its more important but often overlooked role is in medicine – with an interesting history. While native to Madagascar and India, the species was transported throughout the tropics long before there was interest in the plant’s landscape potential. It escaped cultivation and naturalized around the equator. A diversity of cultures, from Madagascar to Jamaica to the Philippines, have a history of using it in folk medicines and especially for treating people with diabetes. It is also known to be poisonous to livestock if ingested in large quantities.

The plant’s therapeutic uses came to the attention of Canadian and American medical researchers during World War II when they learned that soldiers stationed in the Philippines used Madagascar Periwinkle leaves to substitute for unavailable insulin. During the 1950’s, while investigating the effects of Madagascar Periwinkle extracts, the researchers found them to have no appreciable effect on blood sugar levels, but they did reduce the white blood cell count in laboratory animals without significant side effects. More recently, 2 alkaloids in Madagascar Periwinkle leaves, vinblastine and vincristine, were identified as active anti-cancer agents that could be used in chemotherapy. Vinblastine is used for patients with Hodgkin’s disease and vincristine is used for children with leukemia. With the introduction of vincristine, the survival rate for children with leukemia jumped from 20 to 80 percent.

The lesson of the usefulness of this single, once obscure species should not be lost. Madagascar has an incredible number of unique plant and animal species that are becoming extinct at an astonishing rate, as the Malagasy people level natural vegetation to plant crops to feed an exploding population. While one can be sympathetic to their immediate food needs, there are probably many plants with potential medical, industrial, food, or ornamental uses that will disappear before we learn of their value. The tragedy of extinction is that each species is the product of millions of years of evolution that will never be duplicated.